Research On A Parameterized CAD System For The Nose Shape Of High-Speed Trains

Developing high-speed train technologies is an emphasis of modern Chinese railway transportation, while the streamlined design of train nose shape is a main technical mean to improve its aerodynamic performance. To further enhance the level of Chinese high-speed train research & development, design and manufacture, a parameterized CAD system for the nose shape of high-speed trains was developed in this paper on the platform of SolidWorks software by using COM technology in the programming environment of Visual C++, which was on the base of surface modeling technology and parametric technology.A reasonable computer model of the high-speed train nose shape which is a complex space surface is the base of performing related designs, performance analysis & calculations and realizing CAD/CAM. In this paper, the design of high-speed train aerodynamic shapes and the theory of surface modeling were widely researched, and the principles and methods for the design of high-speed train nose shape were analyzed, while the NURBS technology was chosen to build the streamlined surface model.Through the analysis of parametric technology and the CAD application state in railway locomotive and rolling stock industry, SolidWorks, which is an excellent software among the mid-range three-dimensional mechanical design on microcomputer, was chosen as the developing platform for parameterized CAD system for the nose shape of high-speed trains. Based on deeply research on the related technologies of SolidWorks application development, Visual C++ was chosen as the developing environment for the system.According to the characteristics that a NURBS curve in SolidWorks is easy to control and modify, a number of control molded-lines were created on the horizontal section, lateral section and longitudinal section. Then the three-dimensional wire-frame and smooth NURBS surface of the high-speed train nose shape basic outline were constructed. After setting the parametric variables of the driven dimensions and the feature property values, the model database of highspeed train nose shape was established. The DLL plug-in program was driven through SolidWorks API interface. Corresponding model will be called from the surface database and the surface shape will be generated after the outline shape control parameters that were given in the specification were typed into the human-computer interaction dialog boxes.The system that was developed in Visual C++ with the ATL and MFC class library has rich functions and easy to operate/learn with the menu/toolbar of Windows program style, all kinds of dialogs, plenty of hints and good fault-tolerant mechanisms. After completing parameterized computer-aided surface design of high-speed train nose shape, the technical treatments of surface offset, surface thicken and molded lines abstraction on any section of the surface can be performed. Related attachment boundaries can be designed, and the files in IGES format can be exported. Therefore followed designs of shape and plate beam structure, strength/aerodynamic performance analysis can be carried out in other CAD/CAE systems.The system, which is based on the design theory of high-speed train nose shape and integrated the research & development and manufacturing level of Chinese locomotive and rolling stock enterprise, can greatly reduce the workload of train shape and structure design engineers, improve the efficiency of product design and shorten the development cycle so that it has a certain practical value in project application.